Fossil fuels, in particular oil, coal and natural gas, represent the primary sources of energy in today's world. Unfortunately in a world of rapidly increasing energy needs, dependence on any energy source of finite size and limited regional availability has dire consequences for the world's economy. In particular, as a country's need for energy increases, so does its vulnerability to disruption in the supply of that energy source. Additionally, as fossil fuels are the largest single source of carbon dioxide emissions, a greenhouse gas, continued reliance on such fuels can be expected to lead to continued global warming. Accordingly it is imperative that alternative, clean and renewable energy sources be developed that can replace fossil fuels.
Hydrogen-based fuel is currently one of the leading contenders to replace fossil fuel. However in order to successfully transition from oil-based and coal-based fuels to a hydrogen-based fuel, significant improvements must be made in terms of hydrogen production, hydrogen storage and distribution, and hydrogen engines. Clearly the state of the art in each of these developmental areas impacts the other areas. For example, if a method of inexpensively producing hydrogen in small production plants can be developed, production plants can be situated close to the end user, thus avoiding the need for extremely complex and costly distribution systems.
Although a number of techniques can be used to produce hydrogen, the primary technique is by steam reforming natural gas. In this process thermal energy is used to react natural gas with steam, creating hydrogen and carbon dioxide. Although this process is well developed, due to its reliance on fossil fuels and the release of carbon dioxide during production, it does not alleviate the need for fossil fuels nor does it lower the environmental impact of its use over that of traditional fossil fuels. Other, less developed hydrogen producing techniques include (i) biomass fermentation in which methane fermentation of high moisture content biomass creates fuel gas, a small portion of which is hydrogen; (ii) biological water splitting in which certain photosynthetic microbes produce hydrogen from water during their metabolic activities; (iii) photoelectrochemical processes using either soluble metal complexes as a catalyst or semiconducting electrodes in a photochemical cell; (iv) thermochemical water splitting using chemicals such as bromine or iodine, assisted by heat, to split water molecules; (v) thermolysis in which concentrated solar energy is used to generate temperatures high enough to split methane into hydrogen and carbon; and (vi) electrolysis.
Electrolysis as a means of producing hydrogen has been known and used for over 80 years. In general, electrolysis of water uses two electrodes separated by an ion conducting electrolyte. During the process hydrogen is produced at the cathode and oxygen is produced at the anode, the two reaction areas separated by an ion conducting diaphragm. Electricity is required to drive the process. An alternative to conventional electrolysis is high temperature electrolysis, also known as steam electrolysis. This process uses heat, for example produced by a solar concentrator, as a portion of the energy required to cause the needed reaction. Although lowering the electrical consumption of the process is desirable, this process has proven difficult to implement due to the tendency of the hydrogen and oxygen to recombine at the technique's high operating temperatures.
Although a variety of improvements have been devised to improve upon the efficiency of the electrolytic hydrogen production system, to date none of them have been able to make the process efficient enough to make hydrogen-based fuel a viable alternative to fossil fuels. Accordingly, what is needed in the art is a means for efficiently producing hydrogen, the means preferably being small enough to minimize the need for an overly complex distribution system. The present invention provides such a system.